In a thermal power plant or a nuclear power plant, a steam generator etc. generates steam from supplied water, and the generated steam drives a turbine in order to generate electric power. The steam that was used to drive the turbine is treated by a condensate treatment system after the steam is condensed by the condenser, and the condensate is again supplied to the steam generator etc. The condensate treatment system installed in a thermal power plant or a nuclear power plant is required, on the premise that a large amount of condensate can be treated, to remove dissolvable impurities (ionic impurities) in the condensate and to stably ensure the water quality required for the power generating facility. The ionic impurities are generated during normal operations. However, they are also generated when seawater or lake water etc., which is used as cooling water for a condenser, flows into the condensate system due to an unexpected leakage.
Generally, a condensate treatment system has a demineralization tower that removes ionic impurities in the condensate. FIGS. 1A to 1C show examples of prior art demineralization towers that are generally used. FIG. 1A is a sectional view of demineralization tower 101a that is generally used in a pressurized water reactor nuclear power plant or in a thermal power plant. An example is also disclosed in Patent Literature 1. FIG. 1B is a sectional view of demineralization tower 101b that is generally used in a boiling water reactor nuclear power plant. These demineralization towers are generally provided with mixed bed type resin-loaded layer 121a, 121b in which cation exchange resin and anion exchange resin are loaded.
In demineralization tower 101a shown in FIG. 1A, ion exchange resin is loaded in the lower space of demineralization tower 101a. Condensate inlet pipe 111a, i.e., an inlet pipe for condensate to be demineralized, is connected to the upper part of demineralization tower 101a. Water collecting pipes 123 for the condensate, i.e., pipes that collect condensate after it is demineralized, are provided in resin-loaded layer 121a of the ion exchanging resin. Water collecting pipes 123 are made from a plurality of annular pipes and have many water collecting openings formed thereon. Water collecting pipes 123 may be covered with filter cloths. Water collecting pipes 123 are connected to outlet pipes 115a, which extend to the outside of demineralization tower 101a through the bottom of demineralization tower 101a. 
In demineralization tower 101b shown in FIG. 1B, support plate 104 for ion exchange resin is provided in the lower space of demineralization tower 101b. The ion exchange resin is loaded above support plate 104. The space below support plate 104 is not loaded with the ion exchange resin, serving as a space for collecting the demineralized condensate. The lower space is connected to outlet pipe 115b that extends to the outside of demineralization tower 101b through the bottom thereof. FIG. 1C is an enlarged view of part “A” in FIG. 1B. Support plate 104 has many openings 104a formed thereon, and each opening 104a is provided with cap-shaped strainer 135. As also disclosed in Patent Literatures 2 and 3, strainer 135 has strainer member 135b that is circumferentially arranged around shaft 135a and that is fixed, together with fixing jig 135c, to support plate 104 by means of a nut (not shown). Support member 104 may be flat, but alternatively may be formed in a downwardly curved concave in order to reduce the bending stress, as shown by the dashed line shown in FIG. 1B.    Patent Literature 1: JP10-351297A    Patent Literature 2: JP9-24215A    Patent Literature 3: JP7-2414069A    Patent Literature 4: WO2010/16410